How can i clean irregular few group of vertices in sculpting?
Nevermind, I resolved it by myself:
These irregularity are simply bad topology, or rather accumulated vertices that are stacked after an excessive rearrangement of an initial unique mesh. The result is the tangling of groups of vertices that create hollows, ridges and high density of vertices that are hard to handle, and they stay on the bottom.
The use of tools like flatten, smooth, inflate and draw are useless, and also the simplify tool is not helpful.
SOLUTION:
Finally, the direct solution is:

Use in edit mode the tool bisect and trim the piece that has irregularity;
Delete this;
Use a new mesh to sculpt;
End.